A mold for extrusion molding a medical application tube and the extrusion molding method thereof in which the medical application tube having a complex profile can be molded by using a soft thermoplastic resin.
The mold for extrusion molding the medical application tube made of the soft thermoplastic resin provided with flow paths sandwiching the axial portion therein comprises the mold body and the pin including the land portion. The cylindrical rear side mold space for passing the molding material between the inner peripheral surface of the recesses of the mold body and the outer peripheral surface of the pin, and the tip end side mold space including the cross section for forming the medical application tube between the inner peripheral surface of the recess and the land portion of the mold body.
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1. An extrusion mold for a medical application tube made by a soft thermoplastic resin in which a plurality of flow paths by sandwiching the axial portion are formed therein, in which said mold comprises:
a mold body having recess portions penetrating from one end to the other end;
a pin disposed within said recess portions of said mold body for forming a tapered cylindrical rear side mold space for passing a soft thermoplastic resin molding material between the inner peripheral surfaces of said recess portions;
a land portion for forming a tip end side mold space configuring the tip end portion of said pin and including a cross sectional profile for forming said tube for medical tube between the tip end side portion in the inner peripheral surface of said recess portions, in said cross sectional profiles of the tip end side mold spaces formed by the inner peripheral surfaces of said recess portions and the surface of said land portion, the cross sectional profile at the tip end side portion is same as that of said tube for medical tube and the cross sectional profile at the rear side portion is the intermediate profile of that at the tip end portion of the tip end side mold space and that at the rear end side mold space; and
wherein a cross sectional profile of the rear side portion of the tip end side mold space is formed such that each tip end portion of a cross piece is coupled to the ring like inner surface to form four flow pathways, the cross sectional profile of the tip end portion of the tip end side mold space is formed such that a predetermined portion of the ring like portion is notched to communicate at least one of four flow pathways with the outside.
2. The mold for extrusion molding the medical application tube according to
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This application is a divisional application of application Ser. No. 11/961,229, filed Dec. 20, 2007, which claims priority to Japanese Patent Application No. 2006-349617, filed Dec. 26, 2006, the entirety of which is hereby incorporated by reference.
The present invention relates to a mold for extrusion molding a medical application tube employed to drain or supply a medicinal liquid from or to a wound site of a patient and a method for extrusion molding.
In conventional practice, a medical application tube has been used to drain the drainage accumulated in the wound site of a patient. There is a medical application tube comprised by a silicone mold including a basal end side portion having a cylindrical shape and a tip end side portion to be indwelled at the wound site of the patient which is formed into a plurality of flow pathways which are sectioned by a central axis therebetween. Further, to this tip end side portion of the medical application tube, slits are formed by notched the outer peripheral side portions of wall portions forming flow pathways along the axial direction, respectively. By providing these slits, the size of the opening of the medical application tube can be increased to effectively suction the drainage (for example Patent Literature 1: Japanese Patent Examined Publication No. H02-17185).
The cross sectional shape of the tip end side portion of this medical application tube (wound site drain catheter) has four flow paths formed by coupling each tip end portion of a cross piece to the ring shaped inner surface and each of four flow paths are communicated with the outside by forming slits by notching the portions each corresponding to between pieces of the ring. Alternatively, three flow paths are formed by coupling each tip end portion of three pieces extended from the center of the ring in three directions to the ring shaped inner surface and each of three flow paths are communicated with the outside by forming slits formed by notching the portions each corresponding to between pieces of the ring.
Further, when the conventional medical application tube as described above is produced, for example, the tube in which the cross sectional shape of the tip end side portion of this medical application tube (wound site drain catheter) has four flow paths formed by coupling each tip end portion of a cross piece to the ring shaped inner surface is formed by extrusion molding and slits are formed by notching formed by processing the portions each corresponding to between pieces of the ring to form the tube for medical tube or it is carried out to directly extrusion molding the medical application tube having slits.
However, in the method for producing the conventional medical application tube, when the slits are formed by processing, there is a problem in that the production cost is increased. While when the medical application tube is once formed into the final shape thereof by extrusion molding and the molding material thereof is soft resin, since, in general, the sliding between this material and the metallic sleeve of the extrusion mold is not good, it is difficult to form the tube by, for example, vacuum sizing. Moreover, even though the material is soft, when it is silicone resin (non thermoplastic resin), the viscosity thereof is high whereby the shape near the shape of mold space of the extrusion mold can easily be molded, while when the molding material comprised by a soft thermoplastic resin such as soft polyurethane or soft polyvinyl chloride is used, the molding by the conventional extrusion molding, same as in the case of silicone resin, can not be carried out.
The invention has been made in the light of these problems and the object of the invention is to provide a mold for an extrusion molding with which a molding a medical application tube having a complex configuration by using a soft thermoplastic resin and an extrusion molding method can be accomplished.
In order to achieve the above mentioned object, an extrusion mold for the medical application tube in accordance with the invention comprises a soft thermoplastic resin in which a plurality of flow paths made by sandwiching the axial portion are formed therein, in which the mold comprises a mold body having recess portions penetrating from one end to the other end; a pin disposed within said recess portions of said mold body for forming a tapered cylindrical rear side mold space for passing a soft thermoplastic resin molding material between the inner peripheral surfaces of said recess portions; and a land portion for forming a tip end side mold space configuring the tip end portion of said pin and including a cross sectional profile for forming said tube for medical tube between the tip end side portion in the inner peripheral surface of said recess portions, in said cross sectional profiles of the tip end side mold spaces formed by the inner peripheral surfaces of said recess portions and the surface of said land portion, the cross sectional profile at the tip end side portion is same as that of said tube for medical tube and the cross sectional profile at the rear side portion is the intermediate profile of that at the tip end portion of the tip end side mold space and that at the rear end side mold space.
Further, the invention is directed to a method for extruding the medical application tube to mold the medical application tube by using the mold for extrusion molding the medical application tube as set forth above, said method comprises:
a cylinder forming process for forming a molding material into a cylinder by passing the molding material made by a soft thermoplastic resin through the tapered cylindrical rear side mold space provided by placing a pin within the recess of the mold body;
an intermediate profile forming process for forming the cross sectional profile of said molding material formed in said cylinder forming process is configured into the intermediate profile of the ring and the cross sectional profile of the medical application tube at the rear side portion of the tip end side molding space; and
a final profile forming process for shaping the cross sectional profile of the molding material formed in said intermediate profile forming process into the cross sectional profile of the medical application tube at the tip end portion of the tip end side molding space.
The mold for extrusion molding the medical application tube and the extrusion molding method of the first embodiment in accordance with the invention will now be explained in detail with reference to the drawings below.
The medical application tube 10 configured in this way is molded by molding a soft thermoplastic resin of polyurethane with the use of a mold for extrusion molding 20 as shown in
Then, within the bushing holder portion 26, a bushing 27 is disposed and a bushing 28 is placed in front of the bushing 27. The recess 26a formed in the bushing holder portion 26 is formed into a generally cylindrical space having a slightly larger diameter than that of the pin holding hole 25a. With the upper portion of the rear end side portion of that recess 26a, a material pathway 29a extended from a material inlet 29 formed to the upper surface of the pin holder portion 25 is communicated. Further, in the inside of the bushing holder portion 26, a two stepped bushing mounting recess having a slightly small opening at the front surface is provided at the slightly fore side portion therein, and the bushing is disposed in this recess at the deeper side (rear side) thereof.
From the center of the rear end surface through the center of the fore end surface, a frustoconical recess 27a having a large diameter at the rear side and a small diameter at the fore side is formed. The diameter of the rear end portion of this recess 27a is provided so as to be the same as that of the recess 26a. Then, the bushing 28 having a smaller rectangular shape than that of the bushing 27 is disposed at the front side of the bushing mounting recess of the bushing holder portion 26 such that the fore side of the bushing 28 is projected from the bushing holder portion 26. From the center of the rear end surface through the center of the fore end surface of the bushing 28, a narrow cylindrical recess 28a is formed. The recess 28a is provided so as to have a diameter same as that of the diameter at the fore end portion of the recess 27a. Moreover, the pin holding hole 25a, the recess 26a, the recess 27a and the recess 28a are disposed such that the central axis of each of them is in the same line.
The pin 22 comprises a cylindrical fixed portion 22a fixed within the pin holding hole 25a of the pin holder portion 25; a cylindrical straight portion 22b forwardly extending from the fore end of the fixed portion 22a and having a slightly larger diameter and a shorter length in the axial direction than those of the fixed portion 22a; a frustoconical tapered portion 22c forwardly extending from the fore end of the straight portion 22b and having a gradually decreased diameter at the front end side; and a land portion 23. Then, between the outer peripheral surface of the straight portion 22b and the inner peripheral surface of the recess 26a of the bushing holder portion 26, as well as, between the outer peripheral surface of the tapered portion 22c and the inner peripheral surface of the recess 27a of the bushing 27, gaps through which the molding material is traveled are formed, which comprise the rear side mold space of the present invention.
Further, the land portion 23 configuring the tip end portion of the pin 22 is provided at the tip end portion of the tapered portion 22c as shown in
The basal end portion of the land portion 23 is placed to the rear side portion within the recess 28a of the bushing 28 and a cylindrical gap (actually, the thickness of the medical application tube 10 is smaller than that of this gap) having a generally same thickness as that of the outer periphery portion of the medical application tube 10 is provided between the circular portion forming the outer peripheral surface of the basal end portion and the inner peripheral surface of the recess 28a of the land portion 23. Then, this gap forms the rear side portion of the tip end side mold space of the invention. Also, the cross sectional profile of the tip end portion of the land portion 23 is formed to have projections 31a, 31b and 31c provided at each center of arc like portions of the outer peripheral surface of rod like molded portion 23a, 23b and 23c.
The rear end portion of each of projections 31a, 31b and 31c is configured to be an oblique portion such that the portion is increased in the height from the outer peripheral surface of the rod like molded portions 23a, 23b and 23c to forward (in the direction apart from the outer peripheral surface of the rod like molded portions 23, 23b and 23c) with the width gradually increased, and these projections are extended from the tip end portion of the oblique portion to the fore end portion of the rod like molded portion 23a, 23b and 23c with a certain height maintained. To the outer peripheral surface of the rod like molded portion 23d, any projection is provided and the length thereof in the axial direction, as shown in
Then, at the front end surface of the rod like molded portion 23d, the tip end portion of an air outlet 32 extended from the rear side of the pin 22 is opened. The tip end portion 32a of this air outlet 32 is shaped so as to be narrower than the rear side portion 32b and
The plate portion 24, as shown in
At that time, the center portion of the rear surface of the plate portion 24 is contacted with the tip end surface of the rod like molded portions 23a, 23 and 23c as well as the projections 31a, 31b and 31c, respectively, or is provided with a slight gap into which the molding material can not be entered and slits 14a, 14b and 14c are formed to the portions where the projections 31a, 31b and 31c are positioned. According to this, at the center portion of the plate portion 24, a space having the same shape as that of the end surface of the medical application tube 10 comprised by the molding slit 24a and the rod like molded portion 23d is formed. Then, this space and a gap between the tip end side portion of the land portion 23 described in above and the inner peripheral surface of the recess 28a together form the tip end portion of the tip end side mold space of the invention.
Furthermore, the length of the thickness of the plate portion 24 and the length of the tip end projected portion of the rod like molded portion 23d are same to position the tip end surface of the rod like molded portion 23d on the same surface of the front surface of the plate portion 24. An extrusion molding apparatus, though it is not shown in figures, to which the mold for extrusion molding 20 includes various devices or mechanisms required for extrusion molding by the use of the mold for extrusion molding 20, for example, an adapter for connecting the extrusion molding apparatus to the mold for extrusion molding 20 and delivering the molding material from the material inlet 29 to the material path 29a side; a heating cylinder for heating the molding material to be delivered to the material inlet 29; a screw disposed within the heating cylinder; a control device for controlling various devices provided around the mold for extrusion molding; and the like.
When the medical application tube 10 is molded by using the mold for extrusion molding 20 configured in this way, firstly the mold for extrusion molding 20 is heated to the proper temperature, then, the molding material input to the material inlet (not shown) is delivered by the screw with heating it by the heating cylinder to fill it into the material path 29a through the adapter. Next, the molding material is further delivered to travel the molding material from the material path 29a into the rear side mold space. At that time, the molding material is formed into a cylindrical shape by the gap between the inner peripheral surface of the recess 26a of the bushing holder portion 26 and the outer peripheral surface of the straight portion 22b and further deformed into a cylindrical shape having diameter gradually decreased while passing through the gap between the inner peripheral surface of the recess 27a of the bushing 27 and the outer peripheral surface of the tapered portion 22c.
Then, the molding material is traveled from the gap between the inner peripheral surface of the recess 27a of the bushing 27 and the outer peripheral surface of the tapered portion 22c to the rear side portion of the tip end side mold space formed by the inner peripheral surface of the recess 28a of the bushing 28 and the outer peripheral surface of the basal end portion of the land portion 23. According to this, the cylindrical molding material is deformed into the shape in which the cross shaped partition 12 is configured in the cylinder body. Further, the molding material forwardly travels from the rear end portion of the tip end side mold space to enter the gap between the inner peripheral surface of the recess 28a of the bushing 28 and the tip end side portion of the land portion 23 to provide the profile same as the medical application tube 10.
Then, the molding material is extruded from the molding slit 24a of the plate portion 24 to the outside while maintaining that profile and cooled to provide the medical application tube 10. At this extrusion molding, since the molding material is deformed while heated to the proper temperature and traveled from the material path 29a to the molding slit 24a of the plate portion 24, it can be molded without any difficulty. Further, the obtained medical application tube 10 is a mold having an excellent accuracy in dimension.
As described in above, in the mold for extrusion molding the medical application tube and extrusion molding method thereof in accordance with the embodiment of the invention, the molding material input from the material inlet 29 into the material path 29a is formed into a cylindrical shape and, then, once deformed from the cylindrical shape to the profile having the partition 12 in the cylindrical shape rather than the medical application tube 10. Then, the material is deformed to have the final profile of the medial application tube 10 after it is deformed to have the intermediate profile of that cylindrical shape and the profile of the medical application tube 10.
Accordingly, the configuration of the molding material can be gradually changed whereby the medical application tube 10 having a complex profile can be precisely molded even though the sliding property of the molding material is rather bad relative to each portion of the mold for extrusion molding. Further, since the medical application tube 10 provided with slits 14a, 14b and 14c can be molded in one molding process, the need to provide the slits by process after the molding can be eliminated. As a result, the production processes can be decreased to reduce the production cost.
Moreover, the mold for extrusion molding the medical application tube and extrusion molding method thereof in accordance with the embodiment of the invention is not intended to limit to the embodiments described above, various modification thereto can be made within the scope of the invention. For example, in the embodiments described in above, though three slits 14a, 14b and 14c are formed to the medical application tube 10, these slits may be provided to the portion corresponding to the flow path 13d in the outer peripheral portion 11 to communicate all flow paths 13a, 13b, 13c and 13d with the outside. Further, one or two slits may be formed to the medical application tube 10. Moreover, not only four but also a plurality of flow paths may be provided to the medical application tube. Also, the profile of the medical application tube is not limited to the profile of the embodiments described in above may be suitably changed. Further, the soft thermoplastic resin comprising the medical application tube is not limited to polyurethane and other material such as polyvinyl chloride may be employed.
In the mold for extrusion molding the tube for medical tube in accordance with the invention configured in that way described in above, the cross sectional profile at the rear side portion in the cross sectional profiles of the tip end side spaces formed by the inner peripheral surface of the tip end side portion of the recess portions of the mold body and the surface of the land portion configuring the tip end portion of the pin is configured into the intermediate of the cross sectional profile of the medical application tube that is the cross sectional profile at the tip end portion of the tip end side mold space and a ring shape that is the cross sectional profile at the tip end portion of the rear side mold space. Therefore, the molding material is once deformed from the ring shaped cross sectional profile into the intermediate profile near the cross sectional profile of the medical application tube and, then, the intermediate profile can be deformed to the cross sectional profile that is the final profile rather than deforming from the ring shaped cross sectional profile at the rear side mold space formed between the recess portions of the mold body into the cross sectional profile of the tube for medical tube directly.
According to this, the change quantity of the shape by one deformation can be decreased whereby the tube for medical tube having a complex shape can be precisely molded even though the slidability is little or largely bad relative to the mold for the molding material. The medical application tube extruded from the mold for extrusion molding will be slightly extended at the outside of the mold for extrusion molding. Therefore, the size of the cross sectional profile at the tip end portion of the tip end side mold space which is the same as the cross sectional profile of the medical application tube of the invention will be slightly larger than that of the cross sectional profile of the medical application tube.
Another configurational characteristic of the extrusion mold for the medical application tube in accordance with the invention is that a plate part including a recess for forming the outer surface that forms a surface along the outside of the molding material traveled from the rear side mold space is disposed at the tip end side of said recess portions of the mold body, one portion of said land portion is extended to the predetermined position within the recess portion forming the outer surface of said plate part, thereby forming a flow path occluded at the peripheral surface by the medical application tube to be molded in the position where said land portion is located within the plate part, as well as, a space formed by the recess portion forming the outer surface of said plate part and the portion where the land portion is located within the plate part being the tip end portion of the rear side mold space.
In this mold for extrusion molding the medical application tube, a plate part including a recess for forming the outer surface that forms a surface along the outside of the medical application tube is disposed at the tip end side of said recess portions of the mold body, and one portion of a land portion is extended into the outer surface forming recess of this plate part (forward in the axial direction). Therefore, it can be configured that the predetermined flow path in the plurality of flow paths included by the medical application tube is occluded at the peripheral surface other than both ends thereof. One portion of the land part extending into the outer surface forming recess of the plate part in this case may be of several numbers thereof.
According to this, a plurality of flow paths occluded at their peripheral surfaces can be formed to the medical application tube. When the flow path provided with the slit formed to the predetermined portion of the medical application tube is communicated with the outside, the predetermined portion of the land portion is protruded toward the outer peripheral direction to contact with the predetermined portion of the outer surface forming recess of the plate part, or a slight gap into which the molding material can not be entered is formed between that portion and the inner peripheral surface of the outer surface forming recess, thereby forming the slit at that portion. Therefore, the slit is formed to every flow path, the need to provide the plate part can be eliminated.
Yet another configurational characteristic of the extrusion mold for the medical application tube in accordance with the invention is that a cross sectional profile of the rear side portion of the tip end side mold space is formed such that each tip end portion of the cross piece is coupled to the ring like inner surface to form four flow pathways, the cross sectional profile of the tip end portion of the tip end side mold space is formed such that the predetermined portion of the ring like portion is notched to communicate at least one of four flow pathways with the outside. According to this, since an abnormal shaped tube to which slits are provided can be molded by extrusion molding in one time, the need to provide slits by processing after the molding can be eliminated. As a result, the production processes can be reduced to attempt to decrease the manufacturing cost. In this case, the slits formed by notching the ring like portion may be provided with one flow path or 2 to 4 of a plurality of flow path.
Further, the configurational characteristic of the extrusion molding method for molding the medical application tube in accordance with the invention is that the method is the extrusion molding method for molding the medical application tube that molds the medical application tube using the extrusion mold described in above, in which the method comprises a cylinder forming process for forming a molding material into a cylinder by passing the molding material made by a soft thermoplastic resin through the tapered cylindrical rear side mold space provided by placing a pin within the recess of the mold body; an intermediate profile forming process for forming the cross sectional profile of said molding material formed in said cylinder forming process is configured into the intermediate profile of the ring and the cross sectional profile of the medical application tube at the rear side portion of the tip end side molding space; and a final profile forming process for shaping the cross sectional profile of the molding material formed in said intermediate profile forming process into the cross sectional profile of the medical application tube at the tip end portion of the tip end side molding space.
The extrusion molding method for the medical application tube comprised by this way includes the cylinder forming process for forming the molding material into the cylindrical shape; the intermediate profile forming process for forming the cross sectional profile of the cylindrical molding material into the intermediate profile of the ring and the cross sectional profile of the medical tube; and the final profile forming process for shaping the cross sectional profile of the molding material formed in said intermediate profile forming process into the cross sectional profile of the medical application tube. Accordingly, the cross sectional profile of the molding material is deformed from the ring like cross sectional profile of the rear side mold space formed between the recess portion of the mold body and the pin to the intermediate profile near the cross sectional profile of the medical application tube once, then, further deformed to the final profile of the cross sectional profile of the medical application tube from that intermediate profile. Therefore, the change quantity in profile by one deformation of the molding material can be decreased whereby the medical application tube having a complex profile can be precisely molded even though the sliding the material relative to the mold.
Further, the configurational characteristic of the extrusion molding method of the medical application tube in accordance with the invention is that the cross sectional profile of the molding material formed in the intermediate profile forming process is formed into the configuration in which four flow paths are formed by connecting each tip end portion of the cross piece to the ring like inner surface, and the cross sectional profile of the molding material forming in the final profile forming process is configured to the shape in which at least one flow path of four flow paths is communicated with the outside by notching the predetermined portion of the ring like portion. According to this, since an abnormal shaped tube to which slits are provided can be molded by extrusion molding in one time, the need to provide slits by processing after the molding can be eliminated. Further, the production processes can be reduced to attempt to decrease the manufacturing cost.
Abe, Kazuhiro, Ohigawa, Atsushi
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